Protective helmet



FIG. 1 is a top, front perspective view of a protective helmet.

FIG. 2 is a front view of the protective helmet shown in FIG. 1.

FIG. 3 is a left side view of the protective helmet shown in FIG. 1; and,

FIG. 4 is a right side view of the protective helmet shown in FIG. 1.

Portions of the protective helmet and any exemplary environment shown in broken lines are for illustrative purposes only and form no part of the claimed design. 

CLAIM We claim the ornamental design for a protective helmet, as shown and described. 